Supplemental Cash Flow Information - Activities resulting from management of proceeds (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Net change in proceeds managed
Net change in short-term investments	$ (579)	$ 211
Operating cash flow (used) provided	(579)	211
Net change in cash	12	(6)
Net change in proceeds managed	(567)	205
Change in Liabilities for Collateral [Roll Forward]
Liabilities for collateral, beginning of period	(914)	(1,298)
Liabilities for collateral, end of period	(1,481)	(1,093)
Operating cash flow provided (used)	$ 567	$ (205)